TEACHER'S TEACHERS'S TEACHER'S TEACHER'S
Ken Cheney
5:01/C0
Physics 31A Test Five
1. TEMP AND BRIDGES
If a 1,200 meter bridge is built at a temperature of 21 degrees
centigrade, how many meters must be allowed for thermal contraction
when the temperature goes to -15 degrees?
ALPHA=11E-6 1/DEGREES CENTIGRADE
1,200*(21+15)*11E-6
a. .175, b. .29, *c. .475, d. .524, e. 1.42
2. BAGPIPE
A bagpipe produces a steady tone (the drone) in addition to the
"music". Suppose the music beats with the drone to produce subsonic
frequencies which panic the enemy. If the drone is 590 Hz what is the
range of frequencies (in Hz) which will produce subsonic beat
frequencies below 18 Hz?
2*18
a. 554, *b. 36, c. 608, d. 18, e. 16.4
3. SLITHERING
You hear something slithering toward you in the dark. You know
from past experience that somethings slither with a frequency of 130
Hz. If you hear a frequency of 130+17 Hz how fast is the slitherer
slithering toward you (in m/s)? The speed of sound is 300 m/s.
300*(17/(130+17))
*a. 34.7, b. 38.8, c. 83.8, d. 116, e. 149
4. V VS N
A gas is contained in a cylinder with a piston that moves to keep
the pressure constent. The cylinder is in a bath to keep the
temperature constant. Oxygen and hydrogen combine to form water. If
the original volume was 9.1 cubic meters what is the new volume?
9.1*2/3
a. 1.34, b. 2.93, c. 4.16, *d. 6.07, e. 318
5. PIPES 3
How many feet long should a pipe with two open ends be so the
harmonic just higher than the fundamental is 2,800 Hz? Assume the
velocity of sound is 340 f/s. SKETCH!!!! EXPLAIN!!!!
340/2,800
a. .0315, b. .0547, c. .101, *d. .121, e. .266
Physics 31A Test Five - Ken Cheney - V. 5:01/C COPY 0 PAGE 2
6. TIMEKEEPING AND SHM
You wish to construct a spring-weight combination with a one
second period. Your spring stretches .52 meters when you hang a 1.1
newton weight on it. How many kg should you use for the mass to
produce a one second period?
RECALL: PERIOD=2 PI SQUARE ROOT (M/K)
1.1/(4*3.14159*3.14159*.52)
a. .0234, *b. .0536, c. .0609, d. .168, e. .189
7. SHM DERIVATION
Show how a linear restoring force leads to simple harmonic motion.
i.e. F=-kx implies x=A cos( omega t).
8. DURIVE GAS LAW
Durive the Gas Law starting with the force produced by molecules
and ending with PV=nRT. Explain carefully. You can use
proportionalitys instead of integrals during the derivation.